(CNN)—NASA's rockets are astounding machines, capable of blasting into space at thousands of miles per hour and withstanding temperatures twice the melting point of steel. But they can't take off underwater. Rising sea levels caused by melting ice caps threaten to disrupt a handful of NASA launch sites along U.S. coastlines, the space agency warns. In the coming years, launch facilities at Florida's Kennedy Space Center and other places may need to be retrofitted or even moved inland, NASA says. "Every NASA center has its own set of vulnerabilities, and some are more at risk than others," NASA climatologist...